Definition of "destroyer"

That which destroys something.  examples

(military, historical) A small, fast warship with light gun armament, smaller than a cruiser, but bigger than a frigate.

(military) A larger warship with guided missile armament, usually intended for air defence or anti-ship roles. Often, but not always, larger than a frigate and smaller than a cruiser.

1. (science fiction, by extension) A starship of comparable role.  examples